Urticaria, toxic erythema, erythema multiforme, lichen planus, vasculitis and panniculitis are important dermatoses. Urticaria presents as itchy red patches and weals that change shape and last minutes to hours. Toxic erythema appears as an erythematous rash most prominent on the trunk caused by drugs, infections or systemic illnesses. Erythema multiforme features target-like lesions with a dusky purple center and red rim, often on the trunk and palms. Panniculitis is inflammation of subcutaneous fat, seen as erythema nodosum on the shins. Vasculitis

1. Other important dermatoses
Urticaria, toxic erythema,
erythema multiforme, erythema nodosum
vasculitis and lichen planus
Dr Daniel Hewitt
Dermatologist
Skin and Cancer Foundation Westmead

2. Objectives
This module introduces urticaria, toxic
erythema, erythema multiforme, lichen
planus, vasculitis and panniculitis.
The aim is to understand these important
dermatoses – their distinct clinical
features, their causes and their
treatments.

3. Urticaria
This is the presentation of red patches and weals.
Characteristically itchy.
May change shape and last from several minutes to
several hours.

4. Classic examples of urticaria
Classic examples of urticaria

5. Urticaria is the archetypal “dermal” erythema.
There is swelling in the dermis producing a firm, raised
lesion but the epidermis is unaffected. Therefore, there is
no scaling or weeping clinically.

6. Urticaria

7. Pathogenesis
There is a release of histamine and other chemicals from
mast cells. This leads to an increase in vascular
permeability and tissue swelling.
Urticaria may be associated with infections, medications,
physical stimuli or foods. Usually, no particular external
cause is identified.
Most cases do self-resolve and are classififed as acute
urticaria. Chronic urticaria lasts longer than 3 months.
Acute cases are more frequently related to an external
allergen. Chronic urticaria is often due to antibodies
formed by the patient reacting against IgE on their own
mast cells (“auto-antibodies.”)

8. Treatment
Oral antihistamines are the mainstay.
As the pathology is quite deep, topical treatments are
generally of limited benefit.
Oral antihistamines are used as a regular dose. They are
more effective in preventing new wheals forming than in
suppressing widespread weals that are already present.

9. Non-sedating antihistamines are used first-line
eg cetirizine 10mg as a daily morning dose
loratadine 10mg as a daily morning dose
In more resistant cases the dose can be increased to 2 to 3
times the starting dose. This is generally safe, but
patients need to be warned about possible drowsiness.

10. Toxic erythema
This is a characteristic presentation of erythematous
macules and papules. It is usually most prominent on the
trunk.
The apearance is due to dilatation and sometime mild
inflammation of capillaries and arterioles.
This reaction pattern may be described
clinically as “morbilliform” (measles like)
or exanthematous (like a viral exanthem)

11. The causes are numerous but comprise three main groups
Drugs eg antibiotics, thiazides,
anticonvulsants
Infections eg streptococcal infections
viral infections
Systemic causes eg connective tissue
diseases
malignancy

12. A morbilliform toxic erythema

13. Toxic erythema

14. Erythema multiforme
This is a reaction pattern skin with characteristic targetoid
lesions. These have a dusky purple centre, an
oedematous zone and then a red rim. The trunk, limbs
and palms are often affected.
Skin lesions can arise very quickly and patients may be
systemically unwell.
Mucosal surfaces may be involved leading to erosions of
the oral mucosa and conjunctivitis.
It is most often caused by viruses of the herpes family but
can also be triggered by medications.

15. Erythema multiforme

16. Erythema multiforme

17. Panniculitis
This is inflammation of the subcutaneous fat.
Possible causes are pancreatic disease, trauma, cold,
malignancies and connective tissue disease.
There are many different forms of panniculitis, but the most
commonly seen is erythema nodosum.

18. Erythema nodosum presents with painful red nodules on
the shins and occasionally the forearms.
It is most common in young adult women.
The most common causes are
infections streptococcal, especially pharyngitis
viral infections
tuberculosis
medications sulphonamides
salicylates
nonsteroidal anti-inflammatories
sarcoidosis
pregnancy
Sometimes no cause is identified

19. Erythema nodosum

20. Pancreatic panniculitis
Cold panniculitis

21. Vasculitis
This is inflammation of the blood vessels, most
characteristically the post-capillary venules. The form
seen most commonly in the skin is “leukocytoclastic
vasculitis.”
Clinically, the hallmark is palpable purpura. The purpura
represents blood outside blood vessels and the swelling
or palpability occurs because of the oedema developing
due to the inflammation of the blood vessels.
Sometimes larger blood vessels are involved. This has
different manifestations in the skin and the patient is
more likely to have systemic involvement.

22. Leukocytoclastic vasculitis

23. Leukocytoclastic vasculitis

24. The clinical assessment involves assessing for any
systemic involvement (renal, joint, gastrointestinal and
central nervous system) and looking for possible causes.
Leukocytoclastic vasculitis is frequently idiopathic but
causes include
Drugs – antibiotics, especially sulphonamides and
penicillin, thiazide diuretics, anticonvulsants
Infections – streptococcal, hepatitis,
Connective tissue diseases – systemic lupus
erythematosus, rheumatoid arthritis
Malignancies – lymphomas and leukemias

25. Urticarial vasculitis

26. Polyarteritis nodosa

27. Lichen planus
This is an abnormal immune reaction in the skin.
The most characteristic presentation is with purple,
polygonal and flat-topped papules and plaques that are
often pruritic.
Most often these are seen on the volar wrists, lower back
and ankles but can occur anywhere.
There are many other forms eg hypertrophic and mucosal
lichen planus. The lacy white appearance characteristic
on mucosal surfaces are known as Wickham’s striae.
The mouth is involved in 50% of lichen planus involving the
skin. It may be the only area affected.

28. Lichen planus

29. Lichen planus

30. Treatment of lichen planus can be very difficult.
Topical steroids are often first line treatments. Other
treatments include
- Topical calcineurin inhibitors (eg tacrolimus)
- Ultraviolet therapy
- Systemic treatments including acitretin, methotrexate
and prednisolone.

31. Conclusion
Here we have introduced urticaria, toxic erythema,
erythema multiforme, vasculitits, panniculitis and
lichen planus.
These all have characteristic presentations.
Recognizing their clinical presentations is the
first step in diagnosing and managing these
conditions.